Tape based on a superconducting oxide, and method of manufacture

Abstract

A tape based on a superconducting oxide containing Cu-O, the tape being characterized by the fact that it comprises a substrate of flexible metal or composite material having a rectangular cross-section and provided on at least one of its faces with a cavity-free film of perovskite type superconducting oxide having congruent or quasi-congruent melting or peritectic decomposition close to a eutectic point, the thickness of said film lying in the range 1 μm to 100 μm, the orientation of the C axis of the superconducting crystals being perpendicular to said face of said substrate.

I claim: 
     
       1. A tape of a superconducting oxide containing Cu-O made by the process comprising the following steps: (a) preparing a bath of melted superconducting oxide selected from the group consisting of congruent fusion oxides, quasi-congruent fusion oxide and oxides having peritectic decomposition close to an eutectic point;   (b) drawing a substrate of flexible metal having a rectangular transversal cross-section through said bath, vertically from bottom to top at a speed between 1 and 100 cm per minute and depositing on at least one of the faces of said substrate a crystallized film of said melted superconducting oxide having a thickness of between 1 μm to 100 μm;   heat treating said substrate covered with said film, with the orientation of the axis C of the superconducting crystals being perpendicular to said face of said substrate, and the Cu-O planes being oriented in common and parallel to the plane of said face of said substrate, whereby the texture of the film deposited on the substrate is characterized by the absence of cavities therein, thereby conferring a density to the fraction of superconducting material in the film which is equal to its intrinsic density, with the Cu-O planes of the superconducting crystals being oriented in common and parallel to the plane of the face of the substrate resulting in the critical current density Jc of the superconducting film at 77° K. being greater than or equal to 10 4  A/cm 2 , and wherein said super conducting oxide is selected from the group consisting of the Bi-Sr-Ca-Cu-O oxides and the compounds of the Y-Ba-Cu-O family where yttrium is replaced by rare earths such as europium or ytterbium.   
     
     
       2. A tape according to claim 1, wherein the thickness of said substrate lies in the range 25 μm to 100 μm. 
     
     
       3. A method of manufacturing a superconducting oxide-based tape containing Cu-O comprising the steps of: preparing a bath of melted superconducting oxide selected from the group consisting of congruent fusion oxides, quasi-congruent fusion oxides and oxides having peritectic decomposition close to an eutectic point;   drawing a substrate of a flexible metallic material having a rectangular transversal cross-section through said bath vertically from bottom to top at a speed of between 1 and 100 cm per minute, and depositing on at least one of the faces of the substrate, a crystallized film of said melted superconducting oxide having a thickness of between 1 μm and 100 μm;   heat treating said substrate covered with said film, with the orientation of the axis C of the superconducting crystals being perpendicular to said face of the substrate, and with the Cu-O planes being oriented in common and parallel to the plane of said face of said substrate, whereby the texture of the film deposited on the substrate is characterized by the absence of cavities therein, thereby conferring a density to the fraction of superconducting material in the film which is equal to its intrinsic density, with the Cu-O planes of the superconducting crystals being oriented in common and parallel to the plane of the face of the substrate resulting in the critical current density Jc of the superconducting film at 77° K. being greater than or equal to 10 4  A/cm 2 , wherein said superconducting oxide is selected from the group consisting of the Bi-Sr-Ca-Cu-O oxides and the compounds of the Y-Ba-Cu-O family where the yttrium is replaced by rare earths such as europium or ytterbium.   
     
     
       4. The method of manufacture in accordance with claim 3, wherein the thickness of said substrate is between 25 μm and 100 μm.